Adhesion Molecules on Murine Lymphokine‐activated Killer Cells Responsible for Target Cell Killing: A Role of CD2

Lymphokine‐activated killer (LAK) cells were induced from C57BL/6 mouse spleen cells and the effects of culture time on the expression of cell surface phenotypes and cytotoxic activity of LAK cells were determined. The expression of CD2 remarkably decreased after culture of LAK cells for 30 days, while LFA‐1, a principal adhesion molecule in LAK cells, and CD3 were not changed by the culture. LAK cells cultured for 90 days completely lost CD2. In accordance with the decrease of CD2, the cytotoxic activity of LAK cells declined but a certain leven was retained even after the complete loss of CD2. The established LAK cell clones were also strongly positive for the expression of LFA‐1 but negative for CD2. When the LAK cell clones were transfected with the CD2 cDNA, they started to express CD2 on their cell surface and to show greater binding ability and stronger cytotoxicity to target tumor cells. These results indicated that CD2 plays a role as an adhesion molecule responsible for target cell killing in murine LAK cells.